Compilare: main.cpp: In function 'int main()': main.cpp:65:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0; k<ob.size(); k++) ~^~~~~~~~~~ main.cpp:108:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int ind=0; ind<ob.size(); ind++) // 0-3 ~~~^~~~~~~~~~